Multifunctional light, data device, or combination and systems

ABSTRACT

A device including a material including halide perovskite nanocrystals forming a film and configured to receive first electromagnetic radiation having a first wavelength emitted by an excitation source, the first electromagnetic radiation is modulated to include information prior to being received by the material, the material is configured to absorb the first electromagnetic radiation including the information and to emit second electromagnetic radiation having a second wavelength and also including the information, the second wavelength being in the visible range, and the first wavelength of the first electromagnetic radiation is shorter than the visible range; a detector configured to receive the second electromagnetic radiation and to extract the information; and a screen connected to the detector and configured to display the information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/891,621, filed Jun. 3, 2020, which is a continuation of U.S. patentapplication Ser. No. 16/098,575, filed on Nov. 2, 2018, which is a U.S.National Stage Application of International Application No.PCT/IB2017/052442, filed on Apr. 27, 2017, which claims the benefit ofand priority to U.S. Provisional Application Ser. No. 62/335,936, havingthe title “MULTIFUNCTIONAL LIGHT AND DATA DEVICE AND SYSTEM” filed onMay 13, 2016, the disclosures of which are incorporated herein byreference in their entirety.

BACKGROUND

The annual report of the Directorate General for Energy of the EuropeanCommission estimated a 30% increase of the global energy demand by 2030.Out of all the current building electricity consumption, 20% goes forlighting. Thus, it became of paramount importance to find innovativelighting solutions that are multifunctional and more efficient. In thearea of multifunctional devices, especially promising those that cancombine lighting and data transfer. The demand for communication systemsand data transfer, especially wireless technologies, is expected to growat an exponential rate over the next decade. Existing technologiescannot keep up with the surging demand because of their crowded spectraand limited bandwidth.

SUMMARY

Embodiments of the present disclosure provide devices and systemsincluding a material including a halide perovskite and/or phosphor toproduce and/or communicate using visible light, and the like.

In an aspect, a device of the present disclosure, among other, includes:an excitation source and a material including a halide perovskite, aphosphor, or both, wherein the excitation source emits a first lightenergy, wherein the material absorbs the first light energy from theexcitation source and emits a second light energy at a wavelength in thevisible range, wherein the first light energy and the second lightenergy are at different wavelengths. In an embodiment, the halideperovskite can be AMX₃. A can be an organic or inorganic cation, and Mcan be a divalent cation selected from the group consisting of: Pb, Sn,Cu, Ni, Co, Fe, Mn, Pd, Cd, Ge, Cs, or Eu, where X can be selected froma halide. In an embodiment, the excitation source can be a blue laserdiode or blue LED. In an embodiment, the phosphor can be selected fromthe group consisting of: oxides, nitrides, oxynitrides, sulfides,oxysulfides, selenides, halides, oxyhalides, silicates, aluminates,fluoride, phosphates, garnets and scheelites of cerium, dysprosium,erbium, europium, gadolinium, holmium, lanthanum, lutetium, neodymium,praseodymium, promethium, samarium, scandium, terbium, thulium,ytterbium and yttrium.

In an aspect, a system of the present disclosure, among others,includes: an excitation source that emits a first light energy, whereinmodulation of the first light energy encodes a data set, and a materialincluding halide perovskite nanocrystals, a phosphor, or both, whereinthe material absorbs the first light energy from the excitation sourceand emits a second light energy at a wavelength in the visible range,wherein the second light energy encodes the data set. In an embodiment,a detector that receives the second light energy. In an embodiment, thedata set is extracted from the received second light energy. In anembodiment, the data set can be received at about 1 to 3 Gbit/s.

Other compositions, methods, features, and advantages will be or becomeapparent to one with skill in the art upon examination of the followingdrawings and detailed description. It is intended that all suchadditional compositions, methods, features and advantages be includedwithin this description, be within the scope of the present disclosure,and be protected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects of the present disclosure will be more readilyappreciated upon review of the detailed description of its variousembodiments, described below, when taken in conjunction with theaccompanying drawings.

FIGS. 1A-1D illustrate carrier dynamics in CsPbBr₃. (FIG. 1A) ns-TAspectra of CsPbBr₃ NCs in toluene at the indicated delay times. Inset:(FIG. 1A) Absorption (pink) and PL (olive) spectra of CsPbBr₃ NCs intoluene, (FIG. 1B) Transient traces corresponding to the GSB from thens-TA spectra of CsPbBr₃ NCs. (FIG. 1C) fs-TA spectra of CsPbBr₃ NCs.Inset kinetics in 0.0-5.5 ns time window. (FIG. 1D) ns-photoluminescencedecay of CsPbBr₃ NCs monitored at 515 nm. The solid red lines are thebest fits of the kinetic traces.

FIGS. 2A-2B show CsPbBr₃ perovskite nanocrystals for solid statelighting. (FIG. 2A) Spectrum of white light generated using blue laser,green-emitting perovskite NCs and conventional nitride-based redphosphor. Inset: photographs of phosphor with perovskite under ambientlight (right) and generated white light under blue laser (left). (FIG.2B) Generated white light in the CIE 1931 color space (chromaticitycoordinates). For a comparison, single crystal YAG phosphor andBBEHP-PPV+MEH-PPV (75:25) mixture phosphor are also plotted.

FIGS. 3A-D show modulation bandwidth and data transmission measurementsusing perovskite NCs. (FIG. 3A) Schematic drawing of the small-signalfrequency-response measurement setup obtain results in 3B. (FIG. 3B)Measured frequency response of 1) blue LD, 2) laser diode together withphosphor-generated white light, where no optical filter is used 3)phosphor-converted green and red light, where a 500 nm long-pass filteris used; and 4) phosphor-converted red light, where a 550 nm long-passfilter is mounted. (FIG. 3C) Schematic of the data transmissionmeasurement using an OOK scheme used to obtain results in 1D. (FIG. 1D)Bit-error-rates (BERs) at different data rates, with the forward errorcorrection (FEC) limit labelled. Inset: eye diagram of 2 Gbit/s datarate showing with a clear open eye.

FIG. 4A is a high resolution transmission electron microscopy image ofthe CsPbBr₃ perovskite NCs. FIG. 4B is a size distribution histogram ofCsPbBr₃ NCs.

FIG. 5 shows the X-ray diffraction (XRD) spectrum of the NCs exhibitedin the cubic CsPbBr₃ phase.

FIG. 6A shows transient absorption kinetics at 505 nm and FIG. 6B showstime-correlated single-photon counting for CsPbBr₃ NCs solution andfilm.

FIG. 7A shows a photo of the material including CsPbBr₃ perovskitenanocrystals with CdSe/ZnS Quantum Dots phosphor encapsulated in PMMA.FIG. 7B shows a light conversion of blue light into green and red lightsby the material that can be used in LCD backlighting.

FIG. 8A shows a photo of the material including CsPbI₃ perovskitenanocrystals encapsulated in PMMA. FIG. 8B shows a light conversion ofblue light into red light by the material that can be used inhorticultural LED.

DETAILED DESCRIPTION

Before the present disclosure is described in greater detail, it is tobe understood that this disclosure is not limited to particularembodiments described, as such may, of course, vary. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting, since the scope of the present disclosure will be limited onlyby the appended claims.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit (unlessthe context clearly dictates otherwise), between the upper and lowerlimit of that range, and any other stated or intervening value in thatstated range, is encompassed within the disclosure. The upper and lowerlimits of these smaller ranges may independently be included in thesmaller ranges and are also encompassed within the disclosure, subjectto any specifically excluded limit in the stated range. Where the statedrange includes one or both of the limits, ranges excluding either orboth of those included limits are also included in the disclosure.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this disclosure belongs. Although any methods andmaterials similar or equivalent to those described herein can also beused in the practice or testing of the present disclosure, the preferredmethods and materials are now described.

As will be apparent to those of skill in the art upon reading thisdisclosure, each of the individual embodiments described and illustratedherein has discrete components and features which may be readilyseparated from or combined with the features of any of the other severalembodiments without departing from the scope or spirit of the presentdisclosure. Any recited method can be carried out in the order of eventsrecited or in any other order that is logically possible.

Embodiments of the present disclosure will employ, unless otherwiseindicated, techniques of chemistry, material science, synthetic organicchemistry, and the like, which are within the skill of the art. Suchtechniques are explained fully in the literature.

The following examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how toperform the methods and use the compositions and compounds disclosed andclaimed herein. Efforts have been made to ensure accuracy with respectto numbers (e.g., amounts, temperature, etc.), but some errors anddeviations should be accounted for. Unless indicated otherwise, partsare parts by weight, temperature is in ° C., and pressure is in bar.Standard temperature and pressure are defined as 25° C. and 1 bar.

Before the embodiments of the present disclosure are described indetail, it is to be understood that, unless otherwise indicated, thepresent disclosure is not limited to particular materials, reagents,reaction materials, manufacturing processes, or the like, as such canvary. It is also to be understood that the terminology used herein isfor purposes of describing particular embodiments only, and is notintended to be limiting. It is also possible in the present disclosurethat steps can be executed in different sequence where this is logicallypossible.

It must be noted that, as used in the specification and the appendedclaims, the singular forms “a,” “an,” and “the” include plural referentsunless the context clearly dictates otherwise. Thus, for example,reference to “a support” includes a plurality of supports. In thisspecification and in the claims that follow, reference will be made to anumber of terms that shall be defined to have the following meaningsunless a contrary intention is apparent.

GENERAL DISCUSSION

Embodiments of the present disclosure provide devices and systemsincluding a material including a halide perovskite and/or phosphor toproduce and/or communicate using visible light, and the like.Embodiments of the present disclosure provide devices and systemsincluding a material including a halide perovskite and/or a phosphor toproduce visible light and/or communicate using visible light.

Embodiments of the present disclosure include devices and systems canuse the material of the present disclosure in white light for solidstate lighting (SSL) in Liquid Crystal Display (LCD) backlighting systemand in horticultural light emitting diodes (LEDs). In an embodiment,materials of the present disclosure can be used to produce a bright warmwhite light with high CRI and correlated color temperature, which aresuperior relative to other materials.

In another embodiment, materials of the present disclosure can be usedto produce green and red lights with narrow Full Width at Half Maximum(FWHM) and high Photo Luminescence Quantum Yield (PLQY), which aresuperior for LCD backlighting. In another embodiment, materials of thepresent disclosure can be used to produce red light with broad FWHM andhigh PLQY in horticultural LEDs.

In another embodiment, devices and systems can use the materials invisible light communication (VLC, also referred to as Li-Fi), where datais present in the visible light emitted (uses visible light of about 400to 800 THz (about 780-375 nm)) from the device or system and thetransmission can be single or multichannel. In an embodiment, the VLCcan be used in various types of electronics such as cell phones,communication devices, computers screens or monitors, computers, gameconsoles, interactive TV, traffic signals, light bulbs, toys, watches,clothing, digital cameras, incandescent and fluorescent lighting, andthe like. In addition, an embodiment of the present disclosure can beused to communicate (e.g., transmit and/or receive) data using visiblelight communication.

In an embodiment, the device can include an excitation source and thematerial. In an embodiment, the excitation source is a light source suchas a laser, a laser diode, LED or other light source that can operate ina manner desired for the specific application. In an embodiment, thewavelength of the laser can be selected so it is compatible with thematerial and can achieve the desired result. In this regard, the lightsource and the material are each selected to accomplish the desiredresults as described herein. In an embodiment, the light source is ablue laser diode or blue LED.

An embodiment of the present disclosure can include a white solid statelighting (SSL) device. In an embodiment, the SSL can include a LED(Light Emitting Diode). In an embodiment, the material can be disposedon an LED chip, where a power supply for the LED chip and othercomponents normally used in a LED can be present. In addition, the LEDcan include the excitation source, such as a laser diode.

In an embodiment, the excitation source emits a first light energy thatthe material absorbs and then the material emits a second light energyat a wavelength(s) in the visible range. In an embodiment, the firstlight energy and the second light energy are at different wavelengths.In an embodiment, the second light energy is white light that has acolor rendering index of about 80-90 and a correlated color temperatureof about 2000-4000. In another embodiment, the second energy is greenand red lights that has FWHM<35 nm and PLQY>80%. In another embodiment,the second is red light that has FWHM>35 nm and PLQY>60%.

In an embodiment, the material can include a halide perovskite havingthe formula AMX₃ and/or a phosphor. In an embodiment, the halideperovskite can have the following formula: AMX₃. In an embodiment, A canbe a monovalent cation such as alkyl-ammonium (e.g., methylammonium(MA)), formamidinium (FA), 5-ammoniumvaleric acid, or an inorganiccation such Cesium (Cs), or a combination thereof. In an embodiment, Mcan be a cation or divalent cation of an element such as Pb, Sn, Cu, Ni,Co, Fe, Mn, Pd, Cd, Ge, Cs, or Eu. In a particular embodiment, M is Pb.In an embodiment, X can be a halide anion such as CI, Br, F, and I. Inan embodiment, each X can be the same, while in another embodiment, eachX can be independently selected from a halide anion. In particular, X isI or Br or Cl. The selection of the components of AMX₃ is made so thatthe halide perovskite has a neutral charge. In an embodiment, alkyl canrefer to linear or branched hydrocarbon moieties having one to sixcarbon atoms (e.g., methyl, ethyl, propyl, and the like).

In an embodiment, AMX₃ can be: methylammonium lead iodide (MAPbI₃),methylammonium lead bromide (MAPbBr₃), formamidinium lead bromide(FAPbBr₃), formamidinium lead iodide (FAPbI₃), MAPbCl₃, MAPbBr₂Cl,FAPbCl₃, CsPbI₃, CsPbCl₃, CsPbBr₃, FASnBr₃, FASnBr₃, and FASnBr₃,MASnBr₃, MASnBr₃, and MASnBr₃.

In an embodiment, the halide perovskite can be a nanocrystal having adiameter (or longest dimension) of about 3 to 20 nm, about 5 to 10 nm,about 7 to 9 nm, or about 8 nm. In an embodiment, it may be desirable tohave halide perovskite nanocrystals in the range of 2 to 100 nm, and thehalide perovskite nanocrystals can be fabricated according to thedesired use or function.

In an embodiment, the halide perovskite can be mixed with the phosphor.In an embodiment the halide perovskite mixture with the phosphor can beencapsulated into polymer. In an embodiment, the halide perovskite canbe disposed on a phosphor film or vice versa. In an embodiment, theratio of the halide perovskite to the phosphor can be selected toachieve the desired wavelength emission, a high modulation bandwidth,and the like. In an embodiment, the ratio of the halide perovskite tothe phosphor can be about 1:100 to 100:1 or about 1:10 to 10:1.

In an embodiment, the halide perovskite can be nanocrystals and can formmicrocrystalline film on a substrate (e.g., including the phosphor(s)).In an embodiment, the halide perovskite can be a single crystal halideperovskite, microcrystalline halide perovskites or a polycrystallinehalide perovskite. In an embodiment, the halide perovskite can be doped.

In an embodiment, the polymer can be selected from: polyurethanes, latexrubbers, silicon rubbers, other rubbers, polyvinylchloride (PVC), vinylpolymers, polyesters, polyacrylates, polyamides, biopolymers,polyolefines, thermoplastic elastomers, styrene block copolymers,polyether block amid, and combinations thereof.

In an embodiment, the film on a substrate can have a thickness of about5 to 1000 microns, about 100 to 500 micron, about 100 to 300 micron, orabout 200 microns. In an embodiment, the length and width can be on themicron scale to cm scale or larger, and can be designed based on theparticular use. In an embodiment, the halide perovskite can be a singlecrystal halide perovskite. In an embodiment, the halide perovskite canhave cubic-shaped solids having a length, width, and height of about 5to 10 microns.

In an embodiment, the halide perovskite film can be disposed on thesubstrate. In an embodiment, the substrate includes or is the phosphor(e.g., a phosphor film or substrate). In an embodiment, the substratecan have a thickness of about 0.001 to about 10 mm. In an embodiment,the length and width can be on the submicron scale to cm scale orlarger, and can be designed based on the particular use.

An embodiment of the present disclosure includes a method of making afilm or substrate including the phosphor and the halide perovskite. Themethod is simple, the component set up is not complex and does notrequire specialized equipment, the time of reaction is an order ofmagnitude shorter than other methods, and the reaction requires littleenergy input.

In an embodiment, the method of forming the halide perovskite includesdissolving MX₂ and AX in a solvent to form dissolved APbX₃ in acontainer at or near room temperature. The substrate and the solutionare in a container so that the material can form on the substrate. In anembodiment, the solubility can be enhanced using a vortex mixer. In anembodiment, undissolved MX₂ or AX can be filtered out. In an embodiment,A can be an organic cation. In an embodiment, the concentration of theMX₂ can be about 4 to 44 weight %. In an embodiment, the concentrationof the AX can be about 2 to 15 weight %.

In an embodiment, M can be selected from: Pb cation, Sn cation, Cucation, Ni cation, Co cation, Fe cation, Mn cation, Pd cation, Cdcation, Ge cation, or Eu cation, Cs cation, and in a particularembodiment, M can be Pb²⁺. In an embodiment, X can be a halide such asBr⁻, Cl⁻, or I⁻. In an embodiment, A is a cation selected frommethylammonium, formamidinium, and Cesium (Cs).

In an embodiment, the solvent can be N,N-dimethylformamide (DMF),dimethylsulfoxide (DMSO), gamma-butyrolactone (GBL), dichlorobenzene(DCB), N-methilformamide (NMF), aldehydes, ketones, organic acids,ethers, esters, alcohols, hydrocarbons (alkanes, alkenes, alkynes,aromatics etc.), halocarbons, or a combination thereof, depending uponthe AMX₃ structure to be formed.

Subsequently, the mixture in the solvent is heated to a temperature(e.g., about 40 to 150° C.) so that the microcrystalline film (e.g.,APbX₃ structure) forms, where the temperature corresponds to the inversetemperature solubility for dissolved microcrystalline film (e.g.,APbX₃). In an embodiment, the APbX₃ structure can be formed in about0.5-3 h.

In an embodiment, the solvent is matched with the reactants so that atroom temperature the reactants are soluble in the solvent, but at highertemperatures, the APbX₃ structure is formed (e.g., crystalizes). In thisregard, when a MAPbBr₃ perovskite structure is to be formed, the solventused is N,N-dimethylformamide (DMF). In another embodiment, when aMAPbI₃ perovskite structure is to be formed, the solvent isγ-butyrolactone (GBL). In another embodiment, when a MAPbCl₃ perovskitestructure is to be formed, the solvent is dimethylsulfoxide (DMSO) andDMF (1:1 ratio).

In an embodiment, the microcrystalline film (e.g., APbX₃ structure) canbe doped by adding a dopant such as bismuth, gold, indium, tingermanium, phosphine, copper, strontium, cadmium, calcium, and/or nickelions (2+ and 3+ cations as appropriate) to the reaction process by addedthese to the precursor solution. In an embodiment, the atomic of thedopant can be about 0.0001 to 5%.

Embodiments of the phosphor can include those known in the art. In anembodiment, the phosphor can include nitrides, oxynitrides, sulfides,oxysulfides, selenides, halides, oxyhalides, silicates, aluminates,fluoride, phosphates, garnets and scheelites of cerium, dysprosium,erbium, europium, gadolinium, holmium, lanthanum, lutetium, neodymium,praseodymium, promethium, samarium, scandium, terbium, thulium,ytterbium and yttrium, or quantum dots: CdSe, CdSe/ZnS, CdSe/ZnSe,CdSe/CdS, InP, InP/ZnS, InP/ZnSe, PbS, PbSe, CdTe, CdTe/ZnS, CdTe/CdSe,and the like, blends thereof that emit in the orange (e.g., about590-635 nm), yellow (e.g., about 560-590 nm), red (e.g., about 635-700nm), green (e.g., about 510-560 nm), blue (e.g., about 450-490 nm), cyan(e.g., about 490-510 nm), and violet (e.g., about 400-450 nm) wavelengthrange.

In an embodiment, the phosphors or blends of phosphors can be selectedbased on the halide perovskite, the desired wavelength emission, andoptionally on data to be encoded (described in more detail below). In anembodiment, the selection of the phosphor and the halide perovskite canbe done so that the material emits light in the visible wavelength range(and optionally encode data).

In an embodiment, the nitride phosphor can include those that emit lightin the orange, yellow, red, green, blue, cyan, and violet, wavelengthrange. In an embodiment, the phosphor is a red-emitting nitride phosphorwhile the halide perovskite is CsPbBr₃. In an embodiment, the oxynitridephosphor can include those that emit light in the orange, yellow, red,green, blue, cyan, and violet, wavelength range. In an embodiment, theoxide phosphor can include those that emit light hi the orange, yellow,red, green, blue, cyan, and violet, wavelength range. In an embodiment,the sulfide phosphor can include those that emit light in the orange,yellow, red, green, blue, cyan, and violet, wavelength range.

An embodiment of the present disclosure can include a system that canencode a data set using visible light energy. In an embodiment thesystem includes a visible light encoding system and optionally includesa data extracting system (and/or data set decoding system), where thedata extracting feature can be part of the system or part of a separatesystem.

In an embodiment, the visible light encoding system can include anexcitation source that emits a first light energy. In an embodiment, adata set can be encoded into the first light energy by modulating (e.g.,modulation bandwidth of about 400 to 600 MHz, about 450 to 550 MHz, orabout 491 MHz) the first light energy. In other words, the first lightenergy can be modulated over time and/or wavelength to represent thedata set. For example, the first light energy can be modulated (e.g.,turned on/off very fast) to represent “0” and “1” in a way to representthe first data set.

The first light energy is directed at the material including the halideperovskite having the formula AMX₃ and/or the phosphor. The materialabsorbs the first light energy from the excitation source and emits asecond light energy at a wavelength(s) in the visible range, where thesecond light energy (e.g., as a function of time) encodes the data set.In an embodiment, the data set can be transmitted and/or received atabout 0.1 to 5 Gbit/s or about 1 to 3 Gbit/s or to greater than about 3Gbit/s. In an embodiment, the second light energy is white light thathas a color rendering index of about 80-90 and a correlated colortemperature of about 2000-4000.

In an embodiment, the data extracting system can include a detector thatreceives the second light energy. In an embodiment, the detector (e.g.,photodiode or array of photodiodes) can decode the first data set. In anembodiment, the detector can be in communication with a decoding system(e.g., a computer or software system) that can decode the second lightenergy. The data extraction system can be in communication with othersystems that can extract and/or otherwise use the data, for example, acommunication device like a cell phone, a computer, or the like.

EXAMPLES

Now having described the embodiments of the disclosure, in general, theexamples describe some additional embodiments. While embodiments of thepresent disclosure are described in connection with the example and thecorresponding text and figures, there is no intent to limit embodimentsof the disclosure to these descriptions. On the contrary, the intent isto cover all alternatives, modifications, and equivalents includedwithin the spirit and scope of embodiments of the present disclosure.

Example 1

In this disclosure, we investigate the fast and predominantly radiativerecombination characteristics of CsPbBr₃ perovskite nanocrystals (NCs)as a light converter for visible light communication (VLC) in additionto the generation of white light for solid state lighting (SSL). Arecord light converter-associated modulation bandwidth of 491 MHz wasmeasured in our system, which is significantly greater than those ofconventional nitride-based phosphors (3-12 MHz) and organic polymers(200 MHz). The light source generates bright warm white light with highCRI—as much as 89—and a correlated color temperature (CCT) of greaterthan 3200 K. To the best of our knowledge, this work reports the firstVLC system with solution-processed perovskite NCs. This work breaks thebandwidth limitation barrier of phosphor-converted white light VLCsystems and showcases a novel utilization of CsPbBr₃ perovskite NCs asefficient and effective alternative phosphor materials for VLC and SSLapplications simultaneously.

We synthesized CsPbBr₃ perovskite NCs via a modified hot-injectionmethod similar to that presented in previous work (see the experimentalsection). The NCs were characterized by high resolution transmissionelectron microscopy (HRTEM) (FIGS. 4A-B), which revealed uniform cubicshaped NCs with an average size of 8.3±0.8 nm. The X-ray diffraction(XRD) pattern of the NCs exhibited the cubic CsPbBr₃ phase (see FIG. 5). FIG. 1A inset shows the absorption and photoluminescence (PL) spectraof the NCs dispersed in toluene. As can be seen, the absorption spectrumof the CsPbBr₃ NCs does not exhibit any spectral features at wavelengthslonger than ˜520 nm, which is consistent with previous reports. The NCsexhibit a sharp PL emission peak at 512 nm with a narrow full width athalf maximum (FWHM) of 22 nm.

Time-resolved laser spectroscopy has proven to be a critical part ofstudying excited state dynamics. Here, to study the carrier dynamics ofthese CsPbBr₃ NCs, we performed femto-nanoseconds transient absorption(fs-ns-TA) experiments and time-resolved PL measurements and the resultsare presented in FIGS. 1A-D. The ns-TA measurement was recordedfollowing laser pulse excitation at 350 nm with a pump fluence of 9μJ/cm². In this TA experiment, we followed the ground-state bleach (GSB)recovery to monitor the charge recombination dynamics, as shown in FIG.1A. The GSB observed at approximately 505 nm, which corresponds to thesteady-state absorption spectrum, reveals a full recovery in a 30-nstime window with a time constant of 6.4 ns (shown in FIG. 1B). Becauseof the low pump intensity for photo-excitation, Auger recombination dueto carrier multiplication generated by multi-photon absorption is notappreciable. To also confirm that a multiple exciton generation processis not dominant in the observed dynamics, we performed the TAexperiments at two different pump fluencies (9 and 18 μJ/cm²) and almostidentical kinetics are recorded as shown in FIG. 1B.

Additionally, we have performed the fs-TA of CsPbBr₃ NCs and the resultsare shown in FIG. 1C. The GSB recovery shows an additional componentwith a characteristic time constant of 103±40 ps which may be attributedto non-radiation recombination due to surface traps. To furtherunderstand the carrier dynamics and the radiative recombination process,we measured the PL lifetime via time-correlated single-photon counting(TCSPC) using a fluorescence up-conversion spectrometer with excitationat 400 nm (FIG. 1D). The PL lifetime decay profile was collected at 515nm. The decay curve can be fitted with a single exponential functionwith a lifetime of approximately 7.0±0.3 ns. It is worth pointing outthat the PL decay of CsPbBr₃ NCs with two different excitation fluenciesshows a similar decay trend (see FIG. 1D), which is consistent with TAdata. This short lifetime of about 7 ns is comparable with the reportedvalues for similar sized of CsPbBr₃ NCs. We have also observed similarkinetics trend from both solution and film samples of CsPbBr₃ NCs intime-resolved experiments shown in FIGS. 6A-B. Because of their highPLOY of 70±10% and short radiative recombination lifetime of 7.0±0.3 ns,CsPbBr₃ NCs have promising candidates for generating VLC and SSL.

To study the white light generated by utilizing CsPbBr₃ NCs as lightconverters for SSL, a mixture of green-emitting CsPbBr₃ NCs phosphorwith a red-emitting nitride phosphor (LAM-R-6237, Dalian Luming Group)(CsPbBr₃ NCscan be drop casted onto red-emitting phosphor in PDMS(Polydimethylsiloxane) or CsPbBr₃ NCs can be mixed with phosphor andthen encapsulated in PDMS) is excited by a GaN blue-emitting LD (λ=450nm) (see FIG. 2A inset). Operating at 200 mA, the LD generates a warmwhite light (CCT=3236 K) with a CRI value of 89, as calculated after itsemission passes through the phosphor mixture. Compared with the warmwhite LED bulbs available on the market, which have a typical CRI of70-80, the white light generated herein achieves higher quality emissionthat is suitable for lighting. FIGS. 2A-B show the spectrum and thechromaticity diagram (CIE 1931) coordinates (0.3823, 0.3079) of thegenerated white light. The CRI value of the CsPbBr₃ NCs withred-emitting phosphor is also greater than that reported value of 76 fororganic down-converted white VLC transmitters. Our device also showsenhanced performance than commercial WLEDs based on YAG:Ce³⁺ phosphor,which exhibit relatively low CRI (<75) and high CCT (>7765 K). Thedevice using perovskite NCs phosphor as demonstrated in this worksuggests better quality of white light. In comparison, our resultspresent a higher CRI of 89 and a lower CCT of 3236 K, which areessential factors for indoor illuminations and optical displayapplications.

To investigate the modulation bandwidth in CsPbBr₃ NCsphosphor-converted white light, we performed a small-signalfrequency-response measurement (FIG. 3A). A −10 dBm sinusoidal ACmodulation signal was superimposed on a DC bias current to drive the LD.Both the laser emission and phosphor converted light are then collectedby the photodetector. By sweeping the AC modulation frequency from 10MHz to 2 GHz, the response of the overall system response including thephosphor-converted lighting system, is measured by comparing thetransmitted signal and received signal. The modulation bandwidth of theblue LD (B-LD) was measured without phosphor and optical filtersinserted. The frequency response of B-LD+NCs+red-phosphor,NCs+red-phosphor and red-phosphor only was measured by inserting nooptical filter, 500 nm long-pass filter and 550 nm long-pass filter,respectively. Short recombination lifetime is the key parameter for VLCapplications because the capacity of a communications channel is relatedto the bandwidth and lifetime. We posited that due to their desirablecarrier recombination lifetimes, CsPbBr₃ NCs as light convertors havegreat potential for high modulation bandwidth devices and could overcomethe current data transmission bottleneck in slow response (limitedbandwidth) of conventional phosphor-converted WLED. Indeed, we foundCsPbB_(r3) NCs phosphor-converted light exhibits a relatively highbandwidth of 491.4 MHz (FIG. 3B), which is significantly greater thanthose of conventional nitride-based phosphors (˜12.4 MHz), organicmaterials (40-200 MHz), commercial YAG-based phosphors (3-12 MHz) andblue LEDs. In addition to these materials, colloidal quantum dots (CQDs)are also potential wavelength conversion materials for VLC. Leurand et.al. reported that CQDs (core-shell CdSe/ZnS) are capable to generatewhite light when excited by 450 nm blue LED; however, at a considerablylow −3 dB bandwidth of 10˜25 MHz as the carrier relaxation lifetime isconsiderably lower. Using the fast-response CsPbBr₃ NCs as a phosphor,we also demonstrated the data transmission of phosphor-convertedLD-based VLC using an on-off keying (OOK) modulation scheme. The OOK isthe basic form of amplitude shift keying modulation scheme for wirelesscommunication, where the presence or absence of carrier wave representsthe ones and zeros of digital data, respectively. A pseudorandom binarysequence (PRBS) 2¹⁰-1 data-format was used to modulate the laserintensity, thus transmitting data in a wireless manner. The schematic ofthe data transmission measurement by OOK is illustrated in FIG. 3C. TheCsPbBr₃ NCs were deposited on a plastic diffuser to serve as a phosphor.The bit-error-rates (BERs) at variable data rates are demonstrated inFIG. 3D, where a BER of 7.4×10⁻⁵ is measured at 2 Gbit/s. The obtainedBER measurement adheres to the forward error correction (FEC) standard(BER 3.8×10⁻³). The clear open eye as observed in the eye diagram (insetof FIG. 3D) suggests that the CsPbBr₃ NCs phosphor-converted LD VLC iscapable of transmitting a high data rate of up to 2 Gbit/s.

In conclusion, we have demonstrated the CsPbBr₃ NCs' potential to serveas fast color converters for VLC and SSL by mixing them with ared-emitting nitride phosphor. The direct radiative recombination andshort PL lifetime of CsPbBr₃ perovskite NCs enabled us to utilize themas phosphors for dual-function VLC and SSL systems. Because of the shortrecombination lifetime of CsPbBr₃ NCs (relative to conventionalphosphor-based materials), the converted white light (with a high CRI of89 and a low CCT of 3236 K) exhibits an extraordinary modulationbandwidth of 491 MHz, which is 40 times greater than that ofconventional phosphors. The fast response and desirable colorcharacteristics of CsPbBr₃ NCs as a phosphor material pave the way for anew generation of dual-function systems for VLC and SSL with highbrightness and a high Gbit/s data transfer rates.

Example 2

The mixture of CsPbBr₃ perovskite nanocrystals and CdSe/ZnS quantum dotsphosphor encapsulated in PMMA polymer was fabricated. FIG. 7A shows aphoto of the material that includes green emissive CsPbBr₃ NCs and redemissive CdSe/ZnS Quantum Dots Phosphor that are distributed in thepolymer. The PL spectra includes two peaks, the emission of green lightcenters at 510 nm with FWHM=20 nm, the red emission centers at 620 nmwith FWHM=34 nm. The PLQY of the film is 83%.

Because of narrow FWHM (<35 nm) and high PLQY (>80%), this material canbe used for LCD backlighting, where it converts blue light from anexternal source (blue laser or blue LED) into green and red colors.Resulting RGB lights can be directed into LCD matrix to produce adisplay image (FIG. 7B). The advantage of using the present material forLCD backlighting is that it can increase brightness and contrast, widercolor gamut of the display images because of narrow FWHM. Also thematerial will lead to decrease of energy consumption of LCD displaybecause of high PLQY.

Example 3

We fabricated the polymer film containing CsPbI₃ perovskite nanocrystalsin PMMA (FIG. 8A). The PL spectrum includes 1 emission peak that centersat 660 nm, having FWHM=37% and PLQY=68%.

This material can be used for the horticultural LED, where it convertsblue light from an external source (blue laser or blue LED) into redlight (FIG. 8B). The device includes blue LED and the present materialgenerates blue and red lights that are optimal for growing differentplants and crops. Chlorophyll, the most abundant plant pigment, is mostefficient in capturing red and blue light, and other lights are notabsorbed by plants. So ideal light source for plants should illuminatelights in blue and red as the present device. High PLQY (>60%) ensureslow energy consumption of the device. Broad FWHM (>35 nm) ensures thesupply of all range of red light.

It should be noted that ratios, concentrations, amounts, and othernumerical data may be expressed herein in a range format. It is to beunderstood that such a range format is used for convenience and brevity,and thus, should be interpreted in a flexible manner to include not onlythe numerical values explicitly recited as the limits of the range, butalso to include all the individual numerical values or sub-rangesencompassed within that range as if each numerical value and sub-rangeis explicitly recited. To illustrate, a concentration range of “about0.1% to about 5%” should be interpreted to include not only theexplicitly recited concentration of about 0.1 wt % to about 5 wt %, butalso include individual concentrations (e.g., 1%, 2%, 3%, and 4%) andthe sub-ranges (e.g., 0.5%, 1.1%, 2.2%, 3.3%, and 4.4%) within theindicated range. In an embodiment, “about 0” can refer to 0, 0.001,0.01, or 0.1. In an embodiment, the term “about” can include traditionalrounding according to significant figures of the numerical value. Inaddition, the phrase “about ‘x’ to ‘y’” includes “about ‘x’ to about‘y’”.

It should be emphasized that the above-described embodiments of thepresent disclosure are merely possible examples of implementations, andare set forth only for a clear understanding of the principles of thedisclosure. Many variations and modifications may be made to theabove-described embodiments of the disclosure without departingsubstantially from the spirit and principles of the disclosure. All suchmodifications and variations are intended to be included herein withinthe scope of this disclosure.

We claim at least the following:
 1. A device comprising: a materialincluding halide perovskite nanocrystals forming a film and configuredto receive first electromagnetic radiation having a first wavelengthemitted by an excitation source, wherein the first electromagneticradiation is modulated to include information prior to being received bythe material, wherein the material is configured to absorb the firstelectromagnetic radiation including the information and to emit secondelectromagnetic radiation having a second wavelength and also includingthe information, the second wavelength being in the visible range, andwherein the first wavelength of the first electromagnetic radiation isshorter than the visible range; a detector configured to receive thesecond electromagnetic radiation and to extract the information; and ascreen connected to the detector and configured to display theinformation.
 2. The device of claim 1, wherein the halide perovskitenanocrystals are AMX3, wherein A is an organic or inorganic cation, M isa divalent cation selected from the group consisting of: Pb and Sn, andX is selected from a halide.
 3. The device of claim 1, wherein thehalide perovskite nanocrystals are selected from the group consistingof: MAPbI3, MAPbBr3, MAPbCl3, FAPbI3, FAPbBr3, FAPbCl3, CsPbI3, CsPbBr3,CsPbCl3, FASnI3, FASnBr3, FASnCl3, MASnI3, MASnBr3, and MASnCl3, CsSnI3,CsSnBr3, CsSnCl3 wherein MA is methylammonium and FA is formamidinium.4. The device of claim 1, wherein the film comprises a polymer selectedfrom the group consisting of: polyurethanes, latex rubbers, siliconrubbers, other rubbers, polyvinylchloride (PVC), vinyl polymers,polyesters, polyacrylates, polyamides, biopolymers, polyolefines,thermoplastic elastomers, styrene block copolymers, and polyether blockamid.
 5. The device of claim 1, wherein the halide perovskitenanocrystals have a diameter of about 5 to about 1000 nm.
 6. The deviceof claim 1, wherein the film is deposited on a substrate.
 7. The deviceof claim 1, wherein the detector comprises one or more photodiodes. 8.The device of claim 1, further comprising the excitation source.
 9. Asystem, comprising: an excitation source that emits a first lightenergy, a material including a film comprising halide perovskitenanocrystals, wherein the material absorbs the first light energy afterbeing modulated to include information and emits a second light energyat a wavelength in the visible range, including the information, whereinthe first light energy has a wavelength shorter than the visible range;a detector that receives the second light energy and extracts theinformation; and a screen connected to the detector and configured todisplay the information.
 10. The system of claim 9, wherein the halideperovskite nanocrystals are AMX3, wherein A is an organic cation, M is adivalent cation selected from the group consisting of: Pb and Sn, and Xis selected from a halide.
 11. The system of claim 9, wherein the halideperovskite nanocrystals are selected from the group consisting of:MAPbI3, MAPbBr3, MAPbCl3, FAPbI3, FAPbBr3, FAPbCl3, CsPbI3, CsPbBr₃,CsPbCl3, FASnI3, FASnBr3, FASnCl3, MASnI3, MASnBr3, and MASnCl3, CsSnI3,CsSnBr3, CsSnCl3 wherein MA is methylammonium and FA is formamidinium.12. The system of claim 9, wherein the polymer is selected from thegroup consisting of: polyurethanes, latex rubbers, silicon rubbers,other rubbers, polyvinylchloride (PVC), vinyl polymers, polyesters,polyacrylates, polyamides, biopolymers, polyolefines, thermoplasticelastomers, styrene block copolymers, and polyether block amid.
 13. Thesystem of claim 9, wherein the detector comprises one or morephotodiodes.
 14. The system of claim 9, wherein the film is deposited ona substrate.
 15. The system of claim 9, wherein the halide perovskitenanocrystals comprise caesium, copper and iodine.
 16. A devicecomprising: a material including halide perovskite nanocrystals forminga film and configured to receive first electromagnetic radiation havinga first wavelength emitted by an excitation source, wherein the materialis configured to absorb the first electromagnetic radiation from theexcitation source and to emit second electromagnetic radiation having asecond wavelength, the second wavelength being in the visible range, andwherein the first wavelength of the first electromagnetic radiation isshorter than the visible range; and a detector configured to receive thesecond electromagnetic radiation.
 17. The device of claim 16, whereinthe halide perovskite nanocrystals are AMX3, wherein A is an organic orinorganic cation, M is a divalent cation selected from the groupconsisting of: Pb and Sn, and X is selected from a halide.
 18. Thedevice of claim 16, wherein the halide perovskite nanocrystals areselected from the group consisting of: MAPbI3, MAPbBr3, MAPbCl3, FAPbI3,FAPbBr3, FAPbCl3, CsPbI3, CsPbBr3, CsPbCl3, FASnI3, FASnBr3, FASnCl3,MASnI3, MASnBr3, and MASnCl3, CsSnI3, CsSnBr3, CsSnCl3 wherein MA ismethylammonium and FA is formamidinium.
 19. The device of claim 16,wherein the film comprises a polymer selected from the group consistingof: polyurethanes, latex rubbers, silicon rubbers, other rubbers,polyvinylchloride (PVC), vinyl polymers, polyesters, polyacrylates,polyamides, biopolymers, polyolefines, thermoplastic elastomers, styreneblock copolymers, and polyether block amid.
 20. The device of claim 16,wherein the halide perovskite nanocrystals have a diameter of about 5 toabout 1000 nm.